The present invention relates to a mechanically positioned gripping device which is used in the transfer arrangements of sheet-like objects, such as electrodes needed in electrolysis, for transferring objects from one position to another.
During electrolysis, metal is precipitated, by means of electric current, onto the surface of an electrode serving as the cathode. In order to perform the precipitation in an advantageous manner, the electrodes, i.e. the anode and the cathode, should be positioned as near to each other as possible. In large electrolytic tanks, the anodes and cathodes are placed in an alternating fashion. When electrodes must be replaced, for instance in order to recover a precipitate created on the cathode, the replacement is carried out by means of an automatic charging machine which first removes from the tank a desired number of electrodes, such as cathodes, and replaces them with the same number of electrodes. Now, in order to avoid shortcircuits, the charging machine and particularly the gripping device provided in the charging machine must be arranged in an advantageous position with respect to the electrodes for preventing any contact between the electrodes, i.e. the anode and the cathode. In order to avoid said contact, there are designed various different devices utilizing either members attached to the electrolytic tank itself or to a transfer device, said members attempting to adjust the gripping device in an advantageous position.
From the DE patent application Ser. No. 3,508,195, there is known a device where the target of positioning is provided with mechanical guide cones which perform the precise positioning while the gripping device is lowered down. The precise positioning motion takes place on sliding or rolling surfaces that also support the load and the gripping device. Due to this structure, the loading machinery of the transfer arrangement obtains a remarkably bigger loading than the load and the gripping device as such.
In an apparatus according to the Fl patent application No. 870,285, the loading member is provided with a stationary conduit, along which a separate housing moves, supported by the loading machinery. The gripping device is suspended from this housing by means of turnbuckles, and the gripping device is moved in relation to the housing in order to achieve a precise positioning. The separate housing causes an extra load for the loading machinery. The turnbuckles participate in supporting the load and the gripping device, wherefore they must be essentially stronger. Owing to their location, the turnbuckles are short, and the shortening of the turnbuckles in turn leads to worse and worse height alterations and inclinations caused by the positioning movements in connection with the turnbuckle suspension. In the apparatus according to the Fl patent application No. 870,285, said height alterations, and inclinations are directly focused to the gripping device and the load, wherefore the play of positioning remains essentially shorter, and an essentially advanced positioning accuracy is required of the loading member.
From the Fl patent No. 82,435, there is known an automatic charging member for positioning anodes and cathodes in electrolytic tanks. The charging member is provided with members for charging and gripping the load, and with a control frame installed in between the loading member and the gripping device, as well as position sensors for positioning the load. By means of the position sensors, the location of position signs installed in the electrolytic tanks is detected, so that on the basis of the information obtained from the position sensors, the positioning of the gripping device is carried out by moving the control frame. However, the use of position sensors is not possible in all applications.
Moreover, the publications referred to in the above specification do not at all describe how the electrodes immersed in the electrolytic tank are loaded from the electrode handling machine to the transfer system.